Field of the Invention
This application relates to a medical device and more particularly to a retractor system for use in spinal fusion procedures.
Description of the Related Art
Spinal fusion is a surgical technique used to join two or more vertebrae. In most cases, the fusion is augmented by at least one of: placement of an anterior inter-vertebrae fusion device; and a process called fixation, involving the posterior placement of pedicle screws in pedicles of adjacent vertebrae and rods extending between the pedicle screws, to stabilize the vertebrae and facilitate bone fusion.
Access to the anterior inter-vertebral space is required in order to place the anterior inter-body fusion device. There are two ways of accessing the anterior inter-vertebral space. Firstly, it may be accessed through the abdomen, but this procedure may be too invasive. Secondly, it may be approached from posterior, past the spinal cord and the nerve roots.
In establishing access to the anterior inter-body space from posterior, damage may be caused to the spinal structures. To prevent this, a minimal invasive approach is used. However, management of the posterior soft tissue and neural structures during this minimal invasive approach makes access to the anterior inter-vertebral space more challenging. Current devices and procedures or methods provide for retractors for the soft tissue and nerve structures to be anchored to the operating table or to be held by hand by a human operating assistant. These devices and methods are unreliable and potentially dangerous, at least because they are susceptible to relative movement between the body of the patient and the anchor.
In minimal invasive surgical procedures, a tube is connected to the pedicle screw to keep control over the screw during placement in the pedicle and to facilitate insertion of the rod. Hence, the pedicle screw normally forms part of a pedicle screw and releasable tube assembly. Towards the end of the procedure, the tube is released from the screw and removed.
The optimum trajectory for placing the screws is determined by the anatomical features of the pedicles to be linked. Imaginary axial lines through the screws intersect in space. The known tubes are in excess of 100 mm in length, extend along the lines and they often interfere in space, which may lead to inaccurate placement of the pedicle screws. Furthermore, the known assemblies comprise a cumbersome, complex and time consuming mechanism for releasing the tube from the pedicle screw.